Mullen, Common

Plant of the Week

Common Mullen Latin: Verbascum thapsus

Weeds are the bane of a gardener’s existence, but sometimes even weeds can have some
interesting features. Most people with good judgment consider mullen a weed, but I
confess to allowing it to grow in my perennial border when it happens to appear unannounced
and uninvited amongst its more showy brethren.

Mullen is a biennial that grows only leaves the first year and then flowers and dies
the second year. During the first year, it can produce 18-inch long wooly gray leaves
that form a bushel basket-size rosette.

When it flowers in spring of its second season, the rosette stretches out and forms
a spike that grows 5 feet high. The spike will often branch at the top, producing
arms shaped like those of Saguaro cactus of the Arizona desert. Its bright yellow
flowers have five petals. It’s not obvious that the plant is a member of the snapdragon
family.

The common mullen is not native to the United States. It’s an introduced weed from
Eurasia. It was probably introduced during colonial times as a medicinal herb. It’s
leaves have been used as a wrapper – kind of a botanical version of Saran Wrap – for
keeping food from spoiling.

The monks of the Middle Ages grew mullen for a number of ailments, especially those
associated with coughs and congestion. One of its common names was "bullocks lungwort,"
taken from a common home cure used to treat cattle with coughs and pneumonia. Sap
from the crushed leaves of the plant is said to alleviate the pain of insect bites.

But what I find most fascinating about the common mullen is its desire to live. Back
in 1879, Professor William Beal (1833-1924), a botanist at the University of Michigan,
began an experiment that continues to this date. In the fall of that year, Beal collected
seeds of 23 common weeds and placed them in sand in pint jars. The jars were buried
on a sandy knoll in what today is the five-acre W.J. Beal Botanic Garden. Originally,
the jars were dug every five years, but the number of jars began to decline, and now
they’re dug up every 20 years.

The most recent set of jars was dug up in 1999. Most of the seedlings that emerged
after 120 years buried in the cold Michigan soil were the moth mullen, a closely related
species, but the common mullen also made its presence known. These tenacious seeds
remained in a state of suspended animation for more than a century, awaiting their
day in the sun.

Most of Beal’s weed species were real wimps, remaining viable for only 20 years. Only
five species managed to remain viable after 50 years.

Even if you don’t consider mullen a suitable garden plant, we can learn from Professor
Beal’s study. First, every shovelful of soil contains hundreds or maybe even thousands
of seeds, most of which are undesirable. Gardeners should do all they can not to add
to this collection by allowing weeds, or weedy flowers, to go to seed.

Second, most of these long-lived weed seeds need light to germinate, so applying a
mulch as quickly after planting as possible will keep the seed in the dark and reduce
the amount of weeding that will be necessary.

The University of Arkansas Division of Agriculture does not maintain lists of retail
outlets where these plants can be purchased. Please check your local nursery or other
retail outlets to ask about the availability of these plants for your growing area.